In the field of woodworking, glue is often employed to permanently join two or more pieces of wood together. The joining process normally comprises three stages: preparation, gluing/clamping and then finally, conditioning.
The preparation stage itself entails a number of different processes. The woodworker must check that the wood surfaces are clean and of the correct shape. To check the latter condition, he or she test fits the joint by assembling the pieces to be joined without the use of glue. Once the worker is satisfied that the joint surfaces are correctly matched, the pieces are again separated and then placed aside. Next, the required glue, clamps and any other needed tools are collected and placed within ready reach. Finally the work surface, a bench top or tabletop, is cleared and cleaned.
The woodworker then begins the gluing/clamping process. Glue is spread with a brush or similar tool onto all of the surfaces that are to be joined. To facilitate the drying process and to increase the strength of the joint, the glue is allowed to slightly dry on the surfaces until it is tacky. The pieces are then joined together and placed onto the work surface. Next, the pieces of wood are carefully aligned to ensure maximum joint strength and proper appearance. Clamps are then applied to the outside of the work to press the different pieces of wood together and to hold them in place. To apply lateral pressure to the workpiece one or more pipe clamps are placed beneath the joined pieces. These clamps are in the form of a length of pipe having a movable, snubable footpiece at one end and a fixed, movable jaw headpiece at the other end. To apply pressure in a normal direction that is perpendicular to the pipe clamp(s), a number of quick clamps are used. These clamps are placed near the sides of the workpiece and bear down on an elongated block of wood that lies atop the upper face of the workpiece. The latter clamp structure is used to eliminate buckling and warping of the pieces of the wood being joined.
The final step is the conditioning process. In this step, both the glue and the wood are allowed to dry. The glue becomes dry in a number of hours. However, the wood itself can take far longer to dry because it absorbs a significant amount of liquid from the glue during the gluing process. As a result, the wood in the region of the joint becomes swollen for an extended period of time. It can require up to a week for the wood adjacent the joint to dry and to return to its former shape. If the glue assembly is surfaced (planed or sanded) before the excess moisture is removed, permanent depressions will later form in the glued region when the wood returns to its unswollen state.
From the preceding, it can be seen that joining two pieces of wood together is a simple and basic process. However, the joining process requires a significant amount of skill and time to perform correctly.
When joining pieces of wood in a side-to-side fashion such as used for butcher blocks or tabletops, a number of different types of glued joints may be used. A plain side-to-side joint mates a flat edge of one piece of wood to a flat edge of an adjacent piece of wood. To increase the amount of surface area that is coated with glue, shaped joints are often employed. These joints include segments that protrude into the interior of one or more of the joined pieces. Mortise-and-tenon and tongued-and-grooved are common examples of the latter type of glued joint.
There is some controversy over which type of joint is the strongest. A satisfactory glued joint is one in which the strength of the joint is approximately equal to or greater than the strength of the wood being glued. Due to their design and greater surface area, shaped joints have a theoretical advantage over the much simpler to make plain side-to-side joints. However, this advantage is often lost due to inexact shaping of the shaped edges involved. An imperfect matching of surfaces causes poor contact between the wood pieces and creates gaps within the joint which adversely affect the strength of the joint.
In choosing the type of joint to be used, a woodworker weighs a number of factors. Firstly, the amount of time to prepare the edges is considered. A shaped edge takes a significantly greater amount of time to form than a flat edge since it is more complex. Secondly, the time and skill required during the gluing/clamping process is considered. When laying down pieces of wood in side-to-side fashion, the wood often shifts and buckles during the clamping process. A large number of clamps are therefore required to limit this movement and ensure the proper final positioning of the glued pieces. Many woodworkers have found that the use of shaped joints greatly facilitates the clamping process since the joint shape itself tends to maintain the alignment and the position of the wood pieces being joined. This latter factor frequently leads to the woodworker choosing to use a shaped joint in lieu of a plain joint.
Therefore shaped joints, while being more time consuming to manufacture, are often used in lieu of plain side-to-side joints due to the significant time savings realized during the clamping process. There has been a real need in the art for an apparatus that can reduce the time required to clamp a plain side-to-side joint. Such an apparatus would enable a woodworker to use these easier to make joints and still be able to glue and clamp a workpiece in a minimum of time.